The slendertone does not use water based gels like a lot of the other ab devices on the market. They use sticky gel pads. However after 4 to 6 weeks the pads normally need replacing. This is quite a concern for lots of buyers because the kit in the first place is quite expensive, you don’t want to constantly pay a tenner every 4 weeks just to keep the thing going.
There is a very simple and effective way round. The stickiness goes after a few weeks. This is due to dead skin, oils, sweat, fluff etc. Most people will choose to buy a replacement set. Instead just get some rubbing alcohol or even aftershave would do on a cotton tip or cotton wool ball and gently rub the gel patch. This will remove oils etc and render the patch sticky again and you can do this perpetually as long as the patches are not damaged. On my older slendertone device I’m still using the gel patches which I bought in 1992! Just clean it properly with rubbing alcohol or aftershave and you can save a tonne of money